The present invention relates to a magnetic head having good soft magnetic properties.
In magnetic recording and reproducing apparatuses in audiotape recorders, video tape recorders, memory apparatuses of computers, etc., recorded signals have recently been getting higher in density and quality. For higher recording density, metal tapes, vapor deposited tapes, magnetic disks have been developed in which alloy powder composed of Fe, etc. is used as a magnetic recording medium powder. Such magnetic recording media should have high coercivity.
In order that the magnetic recording media having high coercivity can exhibit their own characteristic advantages sufficiently, magnetic heads used for recording should have high saturation magnetic flux densities. Further, when reproduction and recording are conducted by the same heads, cores having high permeability are necessary for such magnetic heads.
However, ferrites conventionally used as core materials have low saturation magnetic flux densities. On the other hand, Permalloy does not have sufficient wear resistance.
Recently, thin layers of an Fe-Al-Si alloy or a Co-Nb-Zr amorphous alloy for magnetic heads have been proposed. The use of such thin layers is reported, for instance, by Shibatani et al. NHK Technical Report Vol. 29 (2), pp. 51-106 (1977), and Hirota et al., Kino Zairyo (Functional Material) Aug. 1986, p. 68.
However, in the Fe-Al-Si alloy thin layer, both magnetostriction .lambda.s and crystal magnetic anisotropy K should be almost zero to obtain high permeability, and the Fe-Al-Si alloy having such composition as to show zero magnetostriction and magnetic anistropy has a saturation magnetic flux density of at most 10-11 kG.
On the other hand, the Co-Nb-Zr amorphous alloy layer having magnetostriction .lambda.s of nearly zero has a saturation magnetic density of at most 12 kG or so.
An alloy layer having a higher saturation magnetic density is now desired for higher recording density, but a sufficiently high saturation magnetic flux density cannot be achieved. Further, attempts have been made to provide an Fe-Si alloy layer having small magnetostriction at high magnetic flux density. In such an alloy layer, when its magnetostriction .lambda.s is zero, its saturation magnetic flux density is about 17.6 kG, higher than those of the above-mentioned alloy layers. However, if its corrosion resistance is intended to be increased, the saturation magnetic flux density of the Fe-Si alloy layer further decreases.
In the meantime, it is required nowadays that a recording medium can have high coercivity and further has high-frequency magnetic characteristics at a high saturation magnetic flux density for high-density recording.
As other alloys having small magnetostriction and high saturation magnetic flux density, Fe-B solid solution alloys described in Japanese Patent Publication No. 58-28341 and Japanese Patent Laid-Open No. 59-100254 are known.
Such alloys are in the form of continuous filament produced by ejecting a melt composed of Fe and B onto a fast rotating surface to rapidly quench the melt at a cooling rate of about 10.sup.4 -10.sup.6 .degree. C./sec. They have saturation magnetization of about 20 kG. These alloys are reportedly suitable for transformers.
However, the Fe-B ribbons produced by such a liquid quenching method are generally difficult to be made thinner than 10 .mu.m and do not have sufficient permeability at high frequency. Also, they do not have sufficient wear resistance and corrosion resistance, which make them unsuitable for magnetic heads, etc.
In addition, such alloys having high saturation magnetic flux densities tend to have low crystallization temperatures, so that crystallization takes place easily if they are kept at temperatures of 500.degree. C. or more for a long period of time in the glass bonding process, causing the deterioration of the magnetic properties. Therefore, their processing conditions are limited.